1. Lecture 13: Carboxylic Acids, Esters, Amines and Amides

2. Book chapter: 14
Pages:

3. Carbon atom of a carbonyl group is attached to a hydroxyl group forming a carboxyl group
As functional group – attached to an alkyl group or an aromatic group

4. IUPAC names Replace e of the alkene with oic acid
If there are substituents – the carbon chain is numbered beginning with the carboxyl carbon

5. Common names of carboxylic acids
Use prefixes: form, acet, propion, butyr
Relate to the natural sources of the simple carboxylic acids

6. Properties of Carboxylic acids
Most polar organic compounds – functional group consists of two polar groups (-OH) and (C=O)
Solubility in water:
Acids with 1-5 C atoms are soluble in water
Length increases – the nonpolar portion reduces the solubility of acid in water
More than 5C atoms – not very soluble in water

7. Acidity of Carboxylic Acids:
Importnat property: ionization in water
Hydrogen ion is transferred to a water molecule – forming of negatively charged cyrboxylate ion and hydronium ion
Generally those acids are more acidic than most other organic compounds
Weak acids; 1% of the acid molecules ionize in water

8. Neutralization of Carboxylic Acids:
Completely neutralized by strong bases (NaOH or KOH)
Products: carboxylate salt and water

9. Chemistry Link to Health: Carboxylic Acids in Metabolism
Several are part of metabolic processes
Example: glucose is broken down into two molecules of pyruvic acid or actually its carboxylate ion pyruvate (glycolysis)
Pyruvic acid is reduced to give lactic acid (lactate ion)

10. Esters Carboxylic acid + alcohol -> ester + water
-H of cyrboxylic acid is replaced by an alkyl group
Esters contained in fats and oils (esters of glycerol and fatty acids)

11. Esterification Production of esters
In the rpesence of an acid catalyst (H2SO4) and heat
-OH group (carboxylic acid) and –H (alcohol) -> combined to form water

12. Naming esters
Two words – derived from the names of the alcohol and the acid
First word – indicates alkyl part from the alcohol
Second word – name of the carboxylate from the carboxylic acid

13. Chemistry Link to Health: Salicylic acid from a Willow Tree
In the past people were chewing the leaves or piece of bark of the willow tree
Relief from pain
Later (1800s)– salicin was discovered
Has carboxyl and hydroxyl group - irritates the stomach lining
1899 – ester of salicylic acid and acetic acid – aspirin
Less irritating, used as analgesic and anti-infammatory agent

14. Esters in plants Fragnances of perfumes and flowers or fruits – esters
Small esters are volatile – smell and soluble in water; taste them

15. Hydrolysis of Esters Acid Hydrolysis
Heating of esters with water in presence of a strong acid
Water reacts with the ester to form a cyrboxylic acid and an alcohol
Reverse of esterification reaction

16. Base Hydrolysis of Esters
Esters undergo hydrolysis with a strong base
Products: Carboxylate salt and corresponding alcohol
Saponification

17. Amines Derivatives of ammonia (NH3)
One or more hydrogen atoms are replaced with alkyl or aromatic groups

18. Naming and Classifying Amines
Common names are often used when alkyl groups bonded to the nitrogen atom are not branched
Groups are listed in alphabetical order
Prefixes di and tri indicate substituents
Classified – by counting the number of C atoms directly bonded to the nitrogen atom

19. Primary (1°) amine – nitrogen bonded to one alkyl group
Secondary (2°) amine – 2 alkyl groups
Tertiary (3°) amine – 3 alkyl groups

20. Aromatic amines Use the name aniline (approved by IUPAC)
Alkyl groups attached to the nitrogen are named with the prefix N- followed by the alkyl name
Aniline – used to make dyes (indigo)
Give color to wool, cotton, silk fibers and blue jeans

21. Skeletal formula Similar like for other organic compounds
We show the hydrogen atoms bonded to the N atom

22. Chemistry Link to Health: amines in Health and Medicine
Histamine – in response to injury or allergy
Causes blood vessels to dilate and increases the permeability of the cells
Redness and swelling in the area
Antihistamines – block the effect of histamine

23. In the body – biogenic amines (hormones)
Carry messages between CNS and nerve cells
Examples: epinephrine (adrenaline) and norepinephrine (noradrenaline)
Released by adrenal medulla in “fight or flight” situations
Raise the blood glucose level and move the blood to the muscles

24. Amphetamines – produced synthetically
Stimulants of the CNS
Also increase cardiovascular activity and depress the appetite
Sometimes used to bring about weight loss; can cause chemical dependency

25. Solubility of amines in water
Contain polar N-H bond – form hydrogen bonds with water
Primary form more bonds with water than secondary
Tertiary only with N atom in the amine

26. Amines react as bases in water:
Ammonia acts as base because it accepts H+ from water
Produces ammonium ion (NH4+) and hydroxide ion (OH-)

27. Ammonium salts:
Example: lemon jiuce on the fish – revomes “fishy” odor by converting amines to their ammonium salts
Neutralization reaction – amines (base) react with an acid to form ammonium salt
Naming: using alkylammonium ion name followed by the name of the negative ion

28. Properties of Ammonium Salts:
Ionic compounds
Solids at room temperature, odorless and soluble in water and body fluids
Amines used as drugs are usually in form of these salts
If it reacts with a strong base – converted back to the amine

29. Heterocyclic amines Cyclic compound
Contains one or more nitrogen atoms in the ring
The heterocyclic amine ring consists of 5 or 6 stoms and one or more nitrogen atoms

30. Chemistry Link to Health: Alkaloids
Active compounds produced by plants
Contain heterocyclic amines
Alkaloid - “alkali-like” or basic characteristics
Some of them used in anesthetics, antidepressants and stimulants
Examples: nicotine and caffeine

31. Several alkaloids – used in medicine
Atropine – from nightshade; used to accelerate slow heart rates
Codeine – poppy plant; painkiller
Heroin – chemical modification of morphine; not used medically (strongly addictive)

32. Amides Derivatives of cyrboxylic acids
Nitrogen replaces hydroxyl grouop

33. Preparation:
Amidation reaction – carboxylic acid reacts with ammonia or primary/secondary amine

34. Naming:
Dropping the oic acid or ic acid and adding the suffix amide
If alkyl group is attached to the nitrogen atom – prefix N- or N,N- precedes the name of the amide

35. Solubility in water:
Do not have properties of bases
Amides with one to five C atoms are soluble in water (they can hydrogen bond with water molecules)
More than five C atoms – effect of hydrogen bonding is diminished; longer carbon chain decreases the solubility

36. Chemistry Link to Health: Amides in Health and Medicine
Simplest amide – urea (end product of protein metabolism)
Removed by kidenys
Malfunction of kidneys – urea is not removed; uremia
Used also as fertilizer to increase nitrogen in the soil

37. Barbiturates – act as sedatives in small dosages or sleep inducers in larger dosages
Aspirin substituetes contain phenacetin – used in Tylenol
Reduces fever and pain, has little anti-inflammatory effect

39. Summary Carboxylic acids Properties of carboxylic acids Esters
Acid/Base Hydrolysis of esters
Amines
Reaction of amines in water
Ammonium salts
Alkaloids
Amides